The invention relates to seats for manual or power cycles and more particularly to seats with thrust backs mounted on vertical seat posts of a cycle. The field of the invention is exemplified by previous patents to co-inventor Holcomb U.S. Pat. No. 3,970,345 issued July 20, 1976 and U.S. Pat. No. 4,141,587 issued Feb. 27, 1979. Each of these cited patents is concerned with cycle seats with upturned seat backs for added thrust for pedalists and added comfort for power cyclists, but each shows contoured seat perimeters to eliminate chafing and provide adequate buttocks support. Now, we have invented apparatus comprising a seat and seat mount that not only provides comfort and thrust efficiency, but also supplies a degree of sprung comfort and adjustability for comfort unattained in prior art devices of this nature, without interference with attachment of cargo carrying apparatus. The inventive seat is capable of fore and aft adjustment to suit long or short legged riders and allows full use of the vertical adjustment inherent in the conventional seat mounting post of bicycles, mopeds and other light-powered cycles. The added comfort is not arrived at at the expense of performance of experts and adds to the enjoyment of casual riders without teaching bad riding habits.